The present invention relates to a recording apparatus capable of recording an image on a recording medium in a plurality of recording modes.
In one of general arrangements for conveying a recording paper sheet in a recording apparatus, a recording paper sheet is fed by rotating conveyance rollers while urging the recording paper sheet against the conveyance rollers. A predetermined recording operation is performed on the fed recording paper sheet (recording sheet) using a recording head. The conveyance rollers are driven by transmitting the drive force of, e.g., a stepping motor via a gear train or the like.
In an arrangement for moving a carriage which carries the recording head, for example, a portion of a timing belt is attached to the carriage, and the belt is driven by, e.g., a stepping motor, thereby moving the recording head, as is well known. With these arrangements, the recording head is scanned with respect to the recording sheet, and a recording operation is performed during the scanning operation using the recording head. Every time a scanning operation is completed, the recording sheet is fed by the recording width of the recording sheet. In this manner, a recording operation for a single recording sheet is performed.
On the other hand, recent recording apparatuses, in particular, the ink-jet recording apparatus, are required to record fine images. As a general arrangement therefor, recording elements in a recording head, e.g., ink ejection orifices in an ink-jet system, are arranged at a high density.
In addition to such a recent tendency, recording apparatuses are required to reduce noise generated upon execution of a recording operation, and to have a high recording speed or to be able to select one of a plurality of recording speeds in accordance with an image to be recorded, so as to improve the values of their commodities.
In order to meet the above-mentioned fine, low-noise, and high-speed recording requirements, the recording sheet conveyance arrangement and the recording head scanning arrangement are improved variously.
However, the conventional recording sheet conveyance arrangement and recording head scanning arrangement responding to various requirements in the recording apparatus suffer from some problems as follows.
1) First, in a conventional recording apparatus, the conveyance speed of a recording sheet remains the same in either a high-speed recording mode for scanning a recording head at a high speed or a normal recording mode for scanning the recording head at a normal scanning speed.
In the high-speed recording mode, in general, an image is formed by thinning out dots constituting the image (draft mode). For this reason, in consideration of an application of such a thinned-out image, the conveyance precision of a recording sheet is not so important, but the speed is rather important.
On the other hand, in the normal recording mode, it is important to improve the conveyance precision so as to record a high-definition image, and to achieve a low-noise arrangement.
However, as described above, in the conventional recording apparatus, the recording sheet conveyance speed remains the same in either the high-speed recording mode or the normal recording mode. For this reason, for example, if the high-speed recording mode is executed at a relatively low conveyance speed to place an importance on, e.g., conveyance precision and low noise, a low-speed recording sheet conveyance operation, which does not match with the high scanning speed of the recording head, is undesirably performed. Conversely, if a relatively high conveyance speed is set in correspondence with the high-speed recording mode, and the normal recording mode is executed, since the conveyance precision is lowered, a fine image cannot be recorded even by a high-density recording head.
2) Second, when a fine-image recording operation is achieved by increasing the density of recording elements of the recording head, the conveyance precision of a recording sheet is required to be improved accordingly. Also, various other requirements for the conveyance speed, and noise upon execution of the conveyance operation must be satisfied.
In a normal recording sheet conveyance operation, if the conveyance amount of the recording sheet is, e.g., "1/6 inch", the drive operation of a stepping motor associated with the conveyance operation is controlled in correspondence with a drive curve having the number of steps of the stepping motor according to the conveyance amount. However, in addition to the normally used conveyance amount, a conveyance operation may often be performed with a still smaller conveyance amount so as to attain, e.g., fine-image recording. In such a case, as one of conventional arrangements, a conveyance operation is performed with the number of steps smaller than that of the above-mentioned drive curve, and the stepping motor is driven at a predetermined pulse rate, i.e., at a predetermined drive speed in correspondence with the smaller number of steps. However, when the drive operation is performed at the predetermined pulse rate (self-start drive without ramp up/down), the drive speed is low, and noise becomes relatively high.
In place of such a drive operation, an arrangement for setting a drive curve according to even a small conveyance amount, and performing a drive operation for conveying a recording sheet in accordance with the set drive curve is known. However, if there are a large number of kinds of such small conveyance amounts, drive curves must be prepared in correspondence with these conveyance amounts, and a control arrangement is complicated very much. Thus, such an arrangement is not practical in consideration of the processing time.
Furthermore, in the above-mentioned arrangement using a drive curve for a small conveyance amount, in order to solve a problem about noise upon execution of the conveyance operation by a small conveyance amount, the drive curve is designed to have symmetrical rising and falling curve patterns, and various conveyance amounts partially use the same rising and falling curve patterns. A constant-speed drive curve having a length according to each conveyance amount is connected between these rising and falling curve patterns.
In this case, a conveyance operation exceeding a predetermined length is controlled based on a drive curve constituted by the entire rising curve pattern, a constant-speed curve pattern, and the entire falling curve pattern. However, since the symmetrical rising and falling curve patterns corresponding to a conveyance operation for a predetermined amount or less are used, the noise, speed, and precision requirements for the recording sheet conveyance operation cannot be sufficiently satisfied in a normal conveyance operation exceeding the predetermined amount.
3) Third, as for the drive operation of the carriage motor for scanning the recording head, the same problem as that described in item 2) above is posed. More specifically, a problem in a short-distance carriage drive operation is posed.
In order to increase the recording speed, a so-called skip operation for scanning the carriage on a blank portion within a line at a higher speed than that in a recording mode is performed. Also, when the carriage is returned, a so-called high-speed return operation for scanning the carriage at a high speed is similarly performed.
With the above-mentioned control, although the recording speed can be increased, sliding noise increases, and recording precision is lowered since the carriage moves at a high speed. In this manner, such control poses a problem in a high-quality mode.
4) Fourth, when an ink-jet system is adopted as a recording system, a capping operation for protecting an ink-jet recording head in a non-recording state, and a wiping operation for maintaining a recording state are performed.
At this time, if a wiping operation is performed scanning the carriage at a high speed, moving noise in the wiping operation is increased, and it is not preferable in some recording modes. On the other hand, if a wiping operation is performed at a low speed, the overall throughput is lowered, and it is not preferable in the high-speed recording mode.
5) Similarly, when an ink-jet system is adopted as a recording system, since the temperature rise rate of the recording head changes depending on the drive state of the ink-jet recording head, in particular, in the high-speed recording mode, the ejection amount of an ink varies, resulting in a density nonuniformity. In addition, the refill time required for refilling an ejected ink in nozzles (ejection portions) cannot be sufficiently assured in the high-speed recording mode.
On the other hand, in a high-quality recording mode, it is demanded to obtain a recording image with a higher density.